This invention relates generally to a liquid dispenser having a pump plunger which reciprocates through an opening in the closure cap of the container for the liquid to be dispensed through a discharge head on the plunger, and more particularly to such a pump in which the pump plunger is locked to the closure cap against relative displacement.
As mentioned in the commonly owned U.S. application Ser. No. 123,168, now U.S. Pat. No. 4,286,736, liquid dispensers of this general type are often provided with some means for locking the plunger against relative displacement. Such locking means may be effected by a threaded engagement between the plunger and the container cap. One of the problems with this type of locking engagement, however, is that unthreading of the plunger during the process of unlocking tends to loosen the cap from the container.
Other plunger immobilization means for liquid dispensers are set forth in U.S. Pat. Nos. 3,797,705, 3,827,605 and 3,827,606 which disclose cam actuated locking fingers and the like. Otherwise, snap locking protective overcaps have been used for locking the plunger against relative displacement.